As development of rotor spinning machines progresses, the goal is not only to improve the quality of the yarns produced but, above all, to increase production capacity. A key factor in increasing production capacity is the rotary speed of the spinning rotor. For this reason, varied kinds of drives and bearings for spinning rotors have been developed, in order to reach rotary speeds of markedly over 100,000 rpm. Reducing the rotor diameter and mass and lowering friction losses enables not only greater rotary speed but also reduced energy consumption when driven.
In this respect, a shaftless spinning rotor, which is embodied as the rotor of an axial field motor, can be considered especially advantageous by providing a combined magnetic and gas bearing which assures relatively low friction losses.
For example, German Patent Publication DE 42 07 673 C1 discloses an axial field motor having a guide magnet arrangement disposed at the center of the rotor and the stator, which generates axial and radial forces and provides a dependable guidance for the spinning rotor. The rotor and stator are kept spaced apart by means of an air or gas cushion emitted from air nozzles associated with the bearing arrangement to act in opposition to the attractive magnetic force. Various factors, such as harmonics in the magnetic field, magnetic and mechanical asymmetries (i.e., imbalances), or transmitted machine vibration, however, can impair the operating uniformity and smoothness of the rotor.